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     GORAD - Geant4 Open-source Radiation Analysis and Design
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First release : September 2020 with Geant4 version 10.7
Author : Makoto Asai (SLAC National Accelerator Laboratory)

Introduction
------------

Gorad (Geant4 Open-sourced Radiation Analysis and Design) is meant to be 
a turn-key application for radiation analysis and spacecraft design built 
on top of Geant4. Simulation geometry should be provided in the form of GDML.
Gorad is controlled by UI commands, and it works both in interactive mode 
with Qt window and in batch mode with an input macro file. 

The current Gorad requires Geant4 version 10.7 (release of December 2020). 
It does not work with earlier version of Geant4. Geant4 has to be installed 
with multithreading mode and GDML interface enabled. Qt is also recommended 
for the use of Gorad in interactive mode. Geant4 GDML interface requires 
Xerces-C++ version 3 or higher. Xerces-C++ has to be compiled with the same 
compiler Geant4 is compiled. Please refer to the Geant4 installation guide 
for enabling these options. 

Building and running Gorad
--------------------------

To compile and run Gorad, all the Geant4 environment variables have to be 
properly set. Use the shell script in the Geant4 installation directory. 
Compilation of Gorad requires cmake and make same as the compilation of 
Geant4 itself.

  $ source $G4INSTALL/bin/geant4.(c)sh
  $ cmake .
  $ make

To run Gorad in interactive mode,

  $ ./gorad

and then, in the keyboard input field, type

  /control/execute <macroFile>

The user may also use any UI commands shown in the left side menu of the 
Qt window. 

To run Gorad in batch mode,

  $ ./gorad <macroFIle>

A sample macro file 
-------------------

Associated macro file "run.mac" can be used for both interactive mode
and batch mode. It uses a simple cone-shaped geometry (simpleCone.gdml)
and King Solar Proton Fluence model (https://doi.org/10.2514/3.62088).
It employs both primary particle generation biasing and geometry
importance biasing. This sample macro file defines a probe filled by
water located at the center of the world volume with dose and flux 
scorers. 

If this sample macro file is used in interactive mode, it also sets up
visualization (through vis.mac). After executing this sample macro, the 
user can start an event loop with /run/beamOn command.

If this sample macro file is used in batch mode, it defines 4 histograms.
After the event loop, These histograms are dumped to corresponding files 
and also plotted to a Postscript file. Scores of the dose and flux scorers 
are also dumped into an output file. In batch mode, this macro executes 
one million events.

Gorad manual and additional GDML file
-------------------------------------

Details of the sample macro file and available alternative commands are
described in the full manual downloadable from the following URL. Also,
additional sample GDML file of partial and simplified Orion Spacecraft 
is available at the following URL. This is a sample input and it is not 
mandatory to execute Gorad.

 https://twiki.cern.ch/twiki/bin/view/Geant4/AdvancedExamplesGorad

Known warning messages while processing a GDML file
---------------------------------------------------

If the input GDML file uses some material names defined in G4NISTManager,
these names are unrecognizable by the GDML perser itself and cause
warning messages. For example

G4GDML: VALIDATION ERROR! ID attribute 'G4_AIR' is referenced but was
        never declared at line: XX

These messages are harmless and these materials are properly interpreted
once they are set to G4LogicalVolume.

Acknowledgements
----------------

Development of Gorad is funded by NASA Johnson Space Center (JSC) under 
the contract NNJ15HK11B.